Field of the Invention
The present invention relates to wireless communications, and more particularly, to a method and apparatus for transmitting an acknowledgement/non-acknowledgement (ACK/NACK) for a narrowband internet-of-things (NB-IoT) in a wireless communication system.
Related Art
3rd generation partnership project (3GPP) long-term evolution (LTE) is a technology for enabling high-speed packet communications. Many schemes have been proposed for the LTE objective including those that aim to reduce user and provider costs, improve service quality, and expand and improve coverage and system capacity. The 3GPP LTE requires reduced cost per bit, increased service availability, flexible use of a frequency band, a simple structure, an open interface, and adequate power consumption of a terminal as an upper-level requirement.
In the future versions of the LTE-A, it has been considered to configure low-cost/low-end (or, low-complexity) user equipments (UEs) focusing on the data communication, such as meter reading, water level measurement, use of security camera, vending machine inventory report, etc. For convenience, these UEs may be called machine type communication (MTC) UEs. Since MTC UEs have small amount of transmission data and have occasional uplink data transmission/downlink data reception, it is efficient to reduce the cost and battery consumption of the UE according to a low data rate. Specifically, the cost and battery consumption of the UE may be reduced by decreasing radio frequency (RF)/baseband complexity of the MTC UE significantly by making the operating frequency bandwidth of the MTC UE smaller.
Narrowband internet-of-things (NB-IoT) is a low power wide area network (LPWAN) radio technology standard that has been developed to enable a wide range of devices and services to be connected using cellular telecommunications bands. NB-IoT is a narrowband radio technology designed for the IoT, and is one of a range of mobile IoT (MIoT) technologies standardized by the 3GPP. NB-IoT focuses specifically on indoor coverage, low cost, long battery life, and enabling a large number of connected devices.
In NB-IoT, ACK/NACK transmission scheme may be different from that of conventional 3GPP LTE. Accordingly, an ACK/NACK transmission method in NB-IoT may be required.